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Big Bang Theory
The Big Bang Theory '''is a scientific theory about how the universe started, and then made the stars and galaxies we see today. The universe began very hot, small, and dense superforce (The mix of the 4 cosmic forces), with no stars, atoms, form, or structure (called a "singularity"). Then about 13.7 billion years ago, space expanded very quickly (thus the name "Big Bang"). This started the formation of atoms, which eventually led to the formation of stars and galaxies. It was Georges Lemaître who first noted (in 1927) that an expanding universe could be traced back in time to an originating single point. The universe is still expanding today, but getting colder as well. As a whole, the universe is growing and the temperature is falling as time passes. Cosmology is the study of how the universe began and its development. Scientists who study cosmology agree that the Big Bang theory matches what they have observed so far. Fred Hoyle called the theory the "Big Bang" on his radio show. He did not believe the Big Bang was correct. Scientists who did not agree with him thought the name was funny and decided to use it. Scientists base the Big Bang theory on many different observations. The most important is the redshift of very far away galaxies. Redshift is the Doppler effect occurring in light. When an object moves away from Earth, its color rays look more similar to the color red than they actually are, because the movement stretches the wavelength of light given off by the object. Scientists use the word "red hot" to describe this stretched light wave because red is the longest wavelength on the visible spectrum. The more redshift there is, the faster the object is moving away. By measuring the redshift, scientists proved that the universe is expanding, and they can work out how fast the object is moving away from the Earth. With very exact observation and measurements, scientists believe that the universe was a singularity approximately 13.8 billion years ago. Because most things become colder as they expand, scientists assume that the universe was very small and very hot when it started. Other observations that support the Big Bang theory are the amounts of chemical elements in the universe. Amounts of very light elements, such as hydrogen, helium, and lithium seem to agree with the theory of the Big Bang. Scientists also have found "cosmic microwaves background radiation". This radiation is known as radio waves, and they are everywhere in the universe. This radiation is now very weak and cold, but a long time ago it was very strong and very hot. It could be said that time had no meaning before the Big Bang. If the Big Bang was the beginning of time, then there was no universe before the Big Bang, since there could not be any "before" if there was no time! Other ideas state that the Big Bang was not the beginning of time 13.8 billion years ago. Instead, some believe that there was a completely different universe before the Big Bang, and it may have been very different from the one we know today. Graphical timeline of the universe Many things happened in the first second of the universe's life: ImageSize = width:720 height:1000 PlotArea = left:40 right:256 bottom:75 top:75 Colors = id:period1 value:rgb(1,1,0.7) # light yellow id:period2 value:rgb(0.7,0.7,1) # light blue id:events value:rgb(1,0.7,1) # light purple id:era1 Value:yellowgreen id:era2 value:lightorange id:time1 Value:coral id:time2 Value:lavender DateFormat = yyyy Period = from:-430 till:155 TimeAxis = format:yyyy orientation:vertical # order:reverse does not work ScaleMajor = unit:year increment:10 start:-430 # second ScaleMinor = unit:year increment:2 start:-430 AlignBars = justify BarData = bar:Clock bar:Era bar:Dummy3 bar:Periods bar:Dummy4 bar:Events TextData = fontsize:M pos:(240,75) text:Planck epoch pos:(250,50) text:Big Bang pos:(20,50) text:"0: Linear time" pos:(10,980) text:"Logarithmic time:" text:"10 · log10 second" pos:(154,946) text:"NEXT" pos:(117,931) text:The Stelliferous Era pos:(245,950) text:"Reionization" LineData = layer:front at:123 frompos:358 tillpos:369 width:0.5 # Matter domination points:(369,878)(402,800) width:0.5 points:(402,800)(413,800) width:0.5 PlotData= textcolor:black fontsize:M width:53 bar:Clock color:events align:right shift:(28,3) mark:(line,teal) at:-120 text:"One picosecond" at:-90 text:"One nanosecond" at:-60 text:"One microsecond" at:-30 text:"One millisecond" at:0 text:"One second" at:36 text:"One hour" at:75 text:"One year" at:105 text:"One thousand years" shift:(43,3) at:135 text:"One million years" width:53 bar:Era mark:(line,white) align:center shift:(0,0) from:-430 till:135 color:era1 text:"The Primordial Era" width:53 bar:Dummy3 width:158 bar:Periods align:center shift:(0,0) mark:(line,white) from:-430 till:-360 color:period1 text:Grand unification epoch from:-360 till:-120 color:period2 text:Electroweak epoch from:-120 till:-60 color:period1 text:Quark epoch from:-60 till:0 shift:(-40,0) align:left color:period2 text:Hadron epoch from: 0 till:23 color:period1 text:Lepton epoch from: 23 till:131 color:period2 text:Photon epoch from:131 till:155 color:period1 text:"Dark Ages" width:53 bar:Dummy4 width:53 mark:(line, blue) textcolor:black fontsize:M bar:Events color:events align:left shift:(30,-4) at:-430 shift:(30,-12) text:"Planck time, the smallest theoretically observable ~unit of time and the time before which science is ~unable to describe the universe. At this point, the ~force of gravity separated from the electronuclear ~force." at:-360 text:"Separation of the strong force from the ~electronuclear force." from:-360 till:-320 align:left shift:(-55,0) color:time1 text:"Inflationary epoch. The Universe expands exponentially" at:-320 shift:(30,4) text:"Reheating after inflation populates universe ~with quarks and anti-quarks." at:-120 text:"The '''weak force separates from the ~electromagnetic force resulting in the four ~separate forces we know today." at:-60 text:"Quarks become confined within hadrons." at:-30 mark:(line,white) text:"Formation of hydrogen nuclei." at:0 text:"Neutrinos cease to interact with other particles." at:23 shift:(30,-11) text:"Lepton/anti-lepton pairs annihilate." from:23 till:31 align:center shift:(0,-4) color:time2 text:"Big Bang nucleosynthesis" at:31 shift:(30,2) text:"3 to 20 minutes: Formation of helium nuclei" from:129 till:131 shift:(-114,-2) color:time1 mark:(line,white) text:"Recombination" # at:123 shift:(30,-32) text:"70,000 years: Matter domination" at:123 mark:(line,white) shift:(30,-83) text:"70,000 years: Matter domination" at:131 text:"379,000 years: Hydrogen and helium nuclei ~capture electrons to form stable atoms. Photons ~are no longer able to interact strongly with atoms. ~Cosmic microwave background radiation streams ~freely." at:155 text:"100 million years: First star begins to shine." Category:Cosmology Category:Astrophysics